Abstract
A measurement was made on the fall velocity of ice crystals at Asahikawa, Hokkaido, in February 1968. The ice crystals were freely falling and drifting in supercooled fog at temperatures of about -20°C. Prevailing forms of the ice crystals were the minute assemblage of plates, the germ of skeleton form and the irregular germ. The fall velocity was measured by the photographs of their trajectories and by the simultaneous observation of wind speed, and it was found that the ice crystals with a mean size of 103 microns fell, as a whole, with vertical speed of 10.7cm•sec-1. This value was compared with the calculated fall velocities of a sphere and a circular disk of the same diameter as the ice crystals observed.
